I cannot hear the distinction between certain sets of vowel sounds. Normally the words in each of these sets (and of several others) all sound identical to me: Don, Dawn; marry, merry, Mary; ah, awe; cot, caught; ferry, fairy. If the speaker's accent heightens the differences between them I might be able to tell them apart, but cannot tell which word is intended by which of the different pronunciations. I can do that only from context.
This may not be uncommon in American English; maps of regional variations in pronunciation suggest that about half of the country pronounce Don and Dawn the same way. This would explain why I hear those names the same way, but only if I lived in that part of the country.
What is this trait called? I wish I knew.
Best Answer
I think we can call it "phonological unawareness". Or it can be related to the different levels of phonological awareness:
It is related with listening skills as well:
Phonics deals with phonological awareness:
That is to say, it is usually mentioned regarding to teaching the language to the children or neurolingustic researches about bilinguals or non-native speakers.
Another source that mentions the term:
And there is more to add to this topic. Phonological history of the English language.
Now that you mention it, we should talk about Mary–marry–merry merger also:
Another useful question: How are 'marry', 'merry', and 'Mary' pronounced differently?